1. Field of the Invention. This invention relates to an electronic power supply and more particularly to a capacitor protection circuit for protecting storage capacitors in the electronic power supply.
2. Description of Related Art. In a typical conventional power supply, an incoming AC voltage is rectified, filtered, and supplied to an inverter circuit. The rectified voltage is typically stored in high energy bulk capacitors before the voltage is supplied to the inverter circuit. The inverter circuit switches the filtered voltage on and off at a high rate to generate a high frequency square wave of a desired voltage level. An output transformer and rectifier circuit then converts the square wave to a desired pulsing DC voltage and passes the pulsing DC voltage through a network of filters and a rectifier to produce a DC voltage output. The DC voltage output of the power supply is regulated by varying the pulse width of the DC voltage generated by the inverter circuit.
An excessive voltage across the bulk capacitors can overstress the bulk capacitors and can cause damage to the power supply by, for example, causing the bulk capacitors to vent or leak electrolyte fluid. The electrolyte fluid may cause a short circuit in the power supply which can cause the power supply to malfunction. The overstressed bulk capacitors may also present a safety or fire hazard. There is, therefore, a need to protect the bulk capacitors from an excessive AC voltage input.